Why Do We Have Time Zones?

What You'll Learn

• The Earth rotates (spins) once every 24 hours, like a spinning top
• Only half of Earth faces the Sun at a time — that half has daytime
• Time zones divide the world into 24 slices so nearby places share the same clock time
• The Prime Meridian in Greenwich, England is the starting line for time zones
• The International Date Line is where the date changes by one day

Words to Know

Time zone

A region where everyone uses the same clock time

"New York and Miami are in the same time zone."

Rotate

To spin around, like a top or a spinning dancer

"The Earth rotates once every 24 hours."

Equator

The imaginary line around the middle of the Earth, like a belt

"The Earth spins fastest at the equator."

Prime Meridian

The starting line for measuring east and west on Earth, in Greenwich, England

"All time zones are counted from the Prime Meridian."

Check What You Learned

Fun Facts

• The Earth rotates once on its axis approximately every 24 hours, creating day and night

  Source: NASA

• The Earth rotates at about 1,000 miles per hour (1,670 km/h) at the equator

  Source: NASA

• Time zones were formally established at the International Meridian Conference in Washington, D.C. in 1884

  Source: Royal Observatory Greenwich

• The Prime Meridian (0 degrees longitude) runs through Greenwich, England and serves as the reference point for time zones

  Source: Royal Observatory Greenwich

• The Earth is divided into 24 standard time zones, one for each hour of the day

  Source: National Geographic

• The International Date Line, located in the Pacific Ocean, is where the calendar date changes by one day

  Source: National Oceanic and Atmospheric Administration